Relay detection method, power conversion device and power equipment

Abstract

The invention relates to a relay detection method applied to a power conversion device. The method comprises the following steps: outputting a first driving signal to the power conversion circuit, wherein the first driving signal is used for controlling the power conversion circuit to output power to the first live wire output end; acquiring a first inverter voltage of the output end of the first live wire; under the condition that the first inversion voltage reaches the target voltage, the zero line relay and the first live wire relay are controlled to be closed; after the zero line relay and the first live wire relay are closed, stopping outputting the first driving signal; and obtaining a first network side voltage of the first live wire input end and a first inversion voltage of the first live wire output end to determine fault detection results of the zero line relay and the first live wire relay. According to the method, faults of the zero line relay and the first live wire relay of the power conversion circuit can be correctly detected, and the reliability of the power conversion circuit is greatly improved.

Description

Technical Field

[0001] This application belongs to the field of power electronics technology, and in particular relates to a relay detection method, a power conversion device, power equipment, and a computer program product. Background Technology

[0002] Power conversion devices (such as inverters) are one of the core components of a power generation system, and their stability directly affects power generation efficiency and the long-term operation of the system. Relays in power conversion devices are responsible for protecting the electrical system from overload, short circuits, and other problems. The normal operation of relays ensures the stable operation of the power conversion device, preventing system shutdown or damage due to overload or other electrical faults. The reliability of relays directly affects the overall operational reliability of the power conversion device. If a relay fails to operate in a timely manner or malfunctions, the power conversion device may continue to operate under fault conditions, or even exacerbate the fault, causing more serious equipment damage. Regularly inspecting relays to ensure accurate and timely operation is a crucial step in ensuring the reliability of the power conversion device.

[0003] In power conversion devices such as split-phase inverters, LCL or LC filters are often used to filter the inverter output to ensure the stability of the output electrical signal. In this case, capacitors are distributed between each live wire (L line) and neutral wire (N line) on the inverter's output side. Due to the presence of these interphase capacitors, even if the N line (neutral line) relay is open-circuited, as long as the relays on the two live wires are functioning normally, the two-phase inverter voltage output by the inverter can still remain normal. This makes it impossible to correctly detect whether the N line relay is faulty. Summary of the Invention

[0004] The purpose of this application is to provide a relay detection method, a power conversion device, an electrical equipment, and a computer program product, aimed at improving the reliability of the power conversion device.

[0005] In a first aspect, embodiments of this application provide a relay detection method applied to a power conversion device; the power conversion device includes a power conversion circuit, a grid-side relay, and an AC power input terminal; the grid-side relay includes a neutral wire relay, a first live wire relay, and a second live wire relay; the first live wire output terminal of the power conversion circuit is connected to the first live wire input terminal of the AC power input terminal through the first live wire relay, the second live wire output terminal of the power conversion circuit is connected to the second live wire input terminal of the AC power input terminal through the second live wire relay, and the neutral wire output terminal of the power conversion circuit is connected to the neutral wire input terminal of the AC power input terminal through the neutral wire relay; the method includes:

[0006] A first drive signal is output to the power conversion circuit, and the first drive signal is used to control the power conversion circuit to output power to the first live wire output terminal;

[0007] Obtain the first inverter voltage at the first live wire output terminal;

[0008] When the first inverter voltage reaches the target voltage, control the neutral wire relay and the first live wire relay to close;

[0009] After both the neutral wire relay and the first live wire relay are closed, the output of the first drive signal stops;

[0010] Obtain the first grid-side voltage at the first live wire input terminal and the first inverter voltage at the first live wire output terminal;

[0011] The fault detection results of the neutral wire relay and the first live wire relay are determined based on the first grid-side voltage and the first inverter voltage.

[0012] In one embodiment, determining the fault detection results of the neutral wire relay and the first live wire relay based on the first grid-side voltage and the first inverter voltage includes:

[0013] When the voltage difference between the first grid-side voltage and the first inverter voltage is greater than the first voltage difference, it is confirmed that at least one of the neutral wire relay and the first live wire relay has an open circuit fault.

[0014] When the voltage difference between the first grid-side voltage and the first inverter voltage is less than the first voltage difference, it is confirmed that neither the neutral wire relay nor the first live wire relay has an open circuit fault.

[0015] In one embodiment, after confirming that there is no open circuit fault in the neutral wire relay and the first live wire relay, the method further includes:

[0016] Control the first live wire relay to disconnect while keeping the neutral wire relay in a closed state;

[0017] A second drive signal is output to the power conversion circuit, and the second drive signal is used to control the power conversion circuit to output power to the first live wire output terminal and the second live wire output terminal.

[0018] When both the first inverter voltage and the second inverter voltage at the second live wire output terminal reach the target voltage, control all grid-side relays to close.

[0019] After all grid-side relays are closed, the output of the second drive signal is stopped;

[0020] Obtain the first grid-side voltage at the first live wire input terminal, the second grid-side voltage at the second live wire input terminal, the first inverter voltage at the first live wire output terminal, and the second inverter voltage at the second live wire output terminal;

[0021] The fault detection result of the second live wire relay is determined based on the first grid-side voltage, the second grid-side voltage, the first inverter voltage, and the second inverter voltage.

[0022] In one embodiment, after outputting the first drive signal to the power conversion circuit, the method further includes: if the first inverter voltage does not reach the target voltage within a first preset time period, then determining that the power conversion circuit is abnormal; and / or after outputting the second drive signal to the power conversion circuit, the method further includes: if the first inverter voltage or the second inverter voltage does not reach the target voltage within a second preset time period, then determining that the power conversion circuit is abnormal.

[0023] In one embodiment, before outputting the first drive signal to the power conversion circuit, the method further includes:

[0024] All network-side relays are kept in the off state.

[0025] Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal;

[0026] When the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold, it is determined that there is a sticking fault in the circuit where the grid-side relay is located.

[0027] In one embodiment, the first live wire relay, the second live wire relay, and the neutral wire relay each include two relays connected in series.

[0028] After determining that there is no adhesion fault in the circuit where the grid-side relay is located, the method further includes:

[0029] Control the closing of all the aforementioned neutral line relays;

[0030] Controlling one of the first fire relays to close and the other to open and / or controlling one of the second fire relays to close and the other to open;

[0031] Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal;

[0032] When the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold, it is confirmed that at least one of the disconnect relays has a sticking fault.

[0033] In one embodiment, the method further includes:

[0034] When the voltage difference between each grid-side voltage and the corresponding inverter voltage is detected to be greater than the first threshold, the two first live wire relays are controlled to be closed and the two second live wire relays are controlled to be open.

[0035] Control one of the two neutral relays to close while the other opens;

[0036] Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal;

[0037] When the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold, it is determined that the disconnected neutral wire relay has a sticking fault.

[0038] In one embodiment, the method further includes:

[0039] After confirming that none of the grid-side relays are stuck together, the step of outputting the first drive signal to the power conversion circuit is performed; and / or

[0040] When the bus voltage of the power conversion circuit is detected to be greater than a preset voltage value, the step of outputting the first drive signal to the power conversion circuit is executed.

[0041] Secondly, embodiments of this application also provide a power conversion device, which includes a power conversion circuit, a grid-side relay, an AC power input terminal, and a controller; the grid-side relay includes a neutral wire relay, a first live wire relay, and a second live wire relay; the first live wire output terminal of the power conversion circuit is connected to the first live wire input terminal of the AC power input terminal through the first live wire relay, the second live wire output terminal of the power conversion circuit is connected to the second live wire input terminal of the AC power input terminal through the second live wire relay, and the neutral wire output terminal of the power conversion circuit is connected to the neutral wire input terminal of the AC power input terminal through the neutral wire relay; the controller is used to execute the relay detection method described above.

[0042] Thirdly, embodiments of this application also provide a power device, including a battery module and a power conversion device as described above; the battery module is used to supply power to the power conversion device or receive power from the power conversion device.

[0043] The beneficial effects of this application embodiment compared with related technologies are as follows: By outputting a first control command, the first phase output inverter voltage of the power conversion circuit is controlled. When the first inverter voltage reaches the target voltage, the neutral wire relay and the first live wire relay are controlled to close. After the neutral wire relay and the first live wire relay are closed, the output of the first drive signal is stopped, that is, the output of the power conversion circuit is stopped. Thus, the fault detection results of the neutral wire relay and the first live wire relay are determined based on the first grid-side voltage at the first live wire input terminal and the first inverter voltage at the first live wire output terminal. The above relay detection method controls the inverter conversion circuit to perform single-phase output, thereby constructing a phase voltage imbalance to detect whether the neutral wire relay is open-circuited. This avoids the problem of failing to correctly detect the neutral wire relay fault due to the presence of the two-phase symmetrical inverter capacitors on the output side of the power conversion circuit when multiple phases are simultaneously open-loop generated, which would otherwise lead to the failure to detect the neutral wire relay fault. The above method can correctly detect the faults of the neutral wire relay and the first live wire relay of the power conversion circuit, greatly improving the reliability of the power conversion circuit. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the power conversion device provided in the embodiments of this application.

[0045] Figure 2 This is a flowchart of a relay detection method provided in an embodiment of this application.

[0046] Figure 3 This is a flowchart of a relay detection method provided in an embodiment of this application.

[0047] Figure 4 This is a schematic diagram of a relay detection device provided in an embodiment of this application.

[0048] Figure 5 This is a schematic diagram of the structure of a power equipment provided in an embodiment of this application. Detailed Implementation

[0049] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0050] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0051] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0052] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0053] This application provides a relay detection method applied to a power conversion device 100. For example... Figure 1 As shown, the power conversion device 100 includes a power conversion circuit 110, a grid-side relay, and an AC power input terminal.

[0054] The power conversion circuit 110 includes an inverter bridge circuit 111, an LCL filter 112, balancing capacitors C11 and C12, and a pre-charge circuit 113. The grid-side relays include a neutral relay 123, a first live relay 121, and a second live relay 122. Taking the power conversion circuit 110 as a split-phase inverter as an example, the AC power supply (e.g., grid) input terminals include a first live input terminal A, a second live input terminal B, and a neutral input terminal N. In other embodiments, the LCL filter 112 can be replaced by an LC filter circuit.

[0055] The inverter bridge circuit 111 includes a first-phase bridge arm and a second-phase bridge arm. The first-phase bridge arm includes power switches Q1 and Q2 connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. The second-phase bridge arm includes power switches Q3 and Q4 connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. Balancing capacitors C11 and C12 are connected in series between the positive DC bus BUS+ and the negative DC bus BUS-. The series connection node of balancing capacitors C11 and C12 serves as the neutral point and also constitutes the neutral output terminal N of the power conversion circuit 110.

[0056] The LCL filter 112 includes a first-phase filter circuit and a second-phase filter circuit. The first-phase filter circuit includes a first inductor L1, a second inductor L2, and a first inverter capacitor C1. The first terminal of the first inductor L1 serves as the first live wire (i.e., the first phase) output terminal of the power conversion circuit 110. The second terminal of the first inductor L1 is connected to the first terminal of the second inductor L2 and the first terminal of the first inverter capacitor C1. The second terminal of the first inverter capacitor C1 is connected to the neutral point of the power conversion circuit 110. The second terminal of the second inductor L2 is connected to the first phase arm of the inverter bridge circuit 111. The second-phase filter circuit includes a third inductor L3, a fourth inductor L4, and a second inverter capacitor C2. The first terminal of the third inductor L3 serves as the second live wire (i.e., the second phase) output terminal of the power conversion circuit 110. The second terminal of the third inductor L3 is connected to the first terminal of the fourth inductor L4 and the first terminal of the second inverter capacitor C2. The second terminal of the second inverter capacitor C2 is connected to the neutral point of the power conversion circuit 110. The second terminal of the fourth inductor L4 is connected to the second phase arm of the inverter bridge circuit 111.

[0057] The first live wire output terminal of the power conversion circuit 110 is connected to the first live wire input terminal A of the AC power input terminal via a first live wire relay 121. The second live wire output terminal of the power conversion circuit 110 is connected to the second live wire input terminal B of the AC power input terminal via a second live wire relay 122. The neutral wire output terminal of the power conversion circuit 110 is connected to the neutral wire input terminal N of the AC power input terminal via a neutral wire relay 123.

[0058] The pre-charge circuit 113 includes current-limiting resistors R1 and R2, pre-charge relays RLY11 and RLY12, and a rectifier bridge DR1. Current-limiting resistor R1 is connected between pre-charge relay RLY11 and the first live wire relay 121, and current-limiting resistor R2 is connected between pre-charge relay RLY12 and the second live wire relay 122. Pre-charge relays RLY11 and RLY12 are also connected to the two AC input terminals of the rectifier bridge DR1, respectively. The positive and negative output terminals of the rectifier bridge DR1 are connected to the positive DC bus BUS+ and the negative DC bus BUS-, respectively.

[0059] In some embodiments, the first live wire relay 121 includes two live wire relays RLY1 and RLY2 connected in series, the neutral wire relay 123 includes two neutral wire relays RLY3 and RLY4 connected in series, and the second live wire relay 122 includes two live wire relays RLY5 and RLY6 connected in series. The precharge relay RLY11 is connected to the series node of live wire relays RLY1 and RLY2 via a current-limiting resistor R1, and the precharge relay RLY12 is connected to the series node of live wire relays RLY5 and RLY6 via a current-limiting resistor R2. It is understood that the connection relationship between the current-limiting resistors R1 and R2, the precharge relays RLY11 and RLY12, and the rectifier bridge DR1 is not limited to the embodiments described above; it is sufficient to ensure that each phase's precharge circuit has a current-limiting resistor, a precharge relay, and a rectifier circuit connected in series.

[0060] The relay testing method provided in this application is used to test the grid-side relays of the power conversion device 100 to ensure the safe and reliable operation of the equipment. This relay control method can be implemented using a separate controller or a controller integrated within the power conversion device 100.

[0061] Please see Figure 2 In some embodiments, the relay detection method includes:

[0062] Step S110: Output a first drive signal to the power conversion circuit. The first drive signal is used to control the power conversion circuit to output power to the first live wire output terminal.

[0063] The first drive signal is used to control the first phase bridge arm of the power conversion circuit 110 to operate, while the second phase bridge arm remains inactive. Typically, before outputting the first drive signal, the voltage on the DC bus needs to reach a certain value, meaning that the balancing capacitors C11 and C12 have completed pre-charging. At this point, the first drive signal can be directly controlled for output. Therefore, before executing step S110, it is necessary to first determine whether the DC bus voltage has reached a certain value or whether the balancing capacitors C11 and C12 have completed pre-charging. Only when these requirements are met will the relay detection method in this embodiment be executed, i.e., step S110 will be executed.

[0064] In this embodiment, the first drive signal is also used to drive the open-loop soft-start ripple of the power conversion circuit 110 until the soft start is completed and the inverter voltage is output to the target value. Soft-start ripple refers to the process of gradually increasing the duty cycle of the drive signal controlling the power switch of the power conversion circuit 110 from 0 or a small value to a preset duty cycle, so as to reduce the current surge to the circuit during the startup process of the power conversion circuit 110.

[0065] Step S120: Obtain the first inverter voltage at the first live wire output terminal. This is achieved by detecting the voltage across the first terminal of the first inductor L1. The first inverter voltage refers to the voltage across the first inverter capacitor C1, and the second inverter voltage refers to the voltage across the second inverter capacitor C2.

[0066] Step S130: When the first inverter voltage reaches the target voltage, control the neutral wire relay and the first live wire relay to close.

[0067] The target voltage is a voltage value that has a small difference from the first grid-side voltage at the first live wire input terminal A, for example, a difference of 0-5V. Under normal circumstances, the first inverter voltage is consistent with the first grid-side voltage. Therefore, regardless of whether the neutral relay 123 and the first live wire relay 121 are closed, the voltage difference between the first inverter voltage and the first grid-side voltage is small, unless the AC power supply GRID fails. Therefore, the fact that the first inverter voltage reaches the target voltage indicates that the power conversion circuit 110 is functioning normally.

[0068] The function of controlling both the neutral wire relay 123 and the first live wire relay 121 to close is used to detect whether the neutral wire relay 123 and the first live wire relay 121 are open circuits.

[0069] In step S140, after both the neutral wire relay and the first live wire relay are closed, the output of the first drive signal is stopped.

[0070] After issuing the control signal to close the neutral wire relay 123 and the first live wire relay 121, a delay is made between the relays' operating time to ensure that the neutral wire relay 123 and the first live wire relay 121 have been engaged. Then, the output of the first drive signal is stopped, effectively shutting down the output of the power conversion circuit 110.

[0071] Step S150: Obtain the first grid-side voltage at the first live wire input terminal and the first inverter voltage at the first live wire output terminal.

[0072] Specifically, after a certain delay following the cessation of the first drive signal output to ensure the complete shutdown of the power conversion circuit 110's output, the first grid-side voltage and the first inverter voltage are then detected. The first grid-side voltage refers to the voltage between the first live wire input terminal A and the neutral wire output terminal N, and the second grid-side voltage refers to the voltage between the second live wire input terminal B and the neutral wire output terminal N.

[0073] Step S160: Determine the fault detection results of the neutral wire relay and the first live wire relay based on the first grid-side voltage and the first inverter voltage.

[0074] If the neutral wire relay 123 and the first live wire relay 121 are open-circuited, the A-phase grid-side circuit of the first inverter voltage cannot be formed. With the output of the power conversion circuit 110 completely shut off, the first inverter voltage will drop rapidly. Therefore, the presence of an open circuit in the live wire relays RLY1 and RLY2, and the neutral wire relays RLY3 and RLY4 can be determined by judging the difference between the first grid-side voltage and the first inverter voltage.

[0075] In this embodiment, only the live wire relay (e.g., the first live wire relay 121) in one phase circuit is engaged to detect the neutral wire relay 123. That is, the other live wire relay (e.g., the second live wire relay 122) remains open, thus creating an imbalance between phases A and B to detect the open circuit of the neutral wire relay 123. If both phase A and phase B relays are engaged, a circuit is formed between phases A and B, resulting in a voltage difference of 240√2sinwt volts. Even if the neutral wire relay 123 is open, because the parameters of the two inverter capacitors (i.e., the first inverter capacitor C1 and the second inverter capacitor C2) are the same, the effective value of the two inverter voltages remains around 120V, making it impossible to determine whether the neutral wire relay 123 is open. Therefore, creating a phase voltage imbalance to detect whether the neutral wire relay is open can avoid the problem of multiple phases of the power conversion circuit 110 simultaneously generating open-loop waveforms, which could lead to the inability to correctly detect the neutral wire relay open circuit fault. The above method can accurately detect faults in the neutral wire relay 123 and the first live wire relay 121 of the power conversion circuit 110, greatly improving the reliability of the power conversion circuit 110.

[0076] It is understood that the relay detection method of this application embodiment can also be used for relay detection in three-phase power conversion circuits.

[0077] In some embodiments, step S160 includes:

[0078] When the voltage difference between the first grid-side voltage and the first inverter voltage is greater than the first voltage difference, it is confirmed that at least one of the neutral wire relay 123 and the first live wire relay 121 has an open circuit fault.

[0079] When the voltage difference between the first grid-side voltage and the first inverter voltage is less than the first voltage difference, it is confirmed that neither the neutral wire relay 123 nor the first live wire relay 121 has an open circuit fault.

[0080] It is understandable that the magnitude of the first voltage difference can be set based on the impedance between the first live wire input terminal A and the first inductor L1. Therefore, if there is an open circuit in the neutral wire relay 123 and the first live wire relay 121, the A-phase grid-side circuit cannot be formed, the first inverter voltage will drop rapidly, and the voltage difference between the first grid-side voltage and the first inverter voltage will be greater than the first voltage difference. In this case, it is determined that at least one of the neutral wire relay 123 and the first live wire relay 121 has an open circuit fault; otherwise, it can be determined that there is no open circuit fault.

[0081] Please see Figure 3 In some embodiments, after confirming that there is no open circuit fault in the neutral wire relay 123 and the first live wire relay 121, step S160 further includes:

[0082] Step S210: Control the first live wire relay to disconnect while keeping the neutral wire relay in the closed state.

[0083] Step S220: Output a second drive signal to the power conversion circuit. The second drive signal is used to control the power conversion circuit to output power to the first live wire output terminal and the second live wire output terminal.

[0084] The second drive signal will simultaneously drive the first phase bridge arm and the second phase bridge arm of the power conversion circuit 110. Similarly, in order to reduce the current surge during startup, a slow-start ripple can be implemented during startup, that is, the duty cycle of the power switch transistor driving the corresponding bridge arm is gradually increased from 0 or a small value to the preset duty cycle.

[0085] Step S230: When both the first inverter voltage and the second inverter voltage at the second live wire output terminal reach the target voltage, control all grid-side relays to close.

[0086] Under normal circumstances, the first inverter voltage is consistent with the first grid-side voltage, and the second inverter voltage is consistent with the second grid-side voltage. Therefore, regardless of whether all grid-side relays are closed, the voltage difference between the first inverter voltage and the first grid-side voltage, and between the second inverter voltage and the second grid-side voltage, is small, unless the AC power grid fails. Therefore, the fact that both the first inverter voltage and the second inverter voltage reach the target voltage indicates that the power conversion circuit 110 is functioning normally.

[0087] In the absence of open circuit faults in the neutral wire relay 123 and the first live wire relay 121, controlling all grid-side relays to close is used to detect whether the second live wire relay 122 is open circuit.

[0088] In step S240, after all grid-side relays are closed, the output of the second drive signal is stopped.

[0089] After issuing a control signal to close all grid-side relays, delay the relays for a certain period of time to ensure that all grid-side relays have been engaged, and stop outputting the second drive signal, that is, turn off the output of the power conversion circuit 110.

[0090] Step S250: Obtain the first grid-side voltage at the first live wire input terminal, the second grid-side voltage at the second live wire input terminal, the first inverter voltage at the first live wire output terminal, and the second inverter voltage at the second live wire output terminal.

[0091] Specifically, after stopping the output of the second drive signal for a certain period of time to ensure that the output of the power conversion circuit 110 is completely turned off, the first grid-side voltage, the second grid-side voltage, the first inverter voltage, and the second inverter voltage are then detected.

[0092] Step S260: Determine the fault detection result of the second live wire relay based on the first grid-side voltage, the second grid-side voltage, the first inverter voltage, and the second inverter voltage.

[0093] If the neutral relay 123 and the first live relay 121 are not faulty, but the second live relay is faulty, the B-phase grid-side circuit of the second inverter voltage cannot be formed, and the second inverter voltage will drop rapidly. Therefore, the presence of a relay fault in live relays RLY5 and RLY6 can be determined by judging the difference between the second grid-side voltage and the second inverter voltage.

[0094] By using open-loop waveform generation, the grid-side circuit of phase A is first connected to create a phase voltage imbalance to detect whether the neutral relay is open-circuited. This avoids the problem of distributed voltage generated by inverter capacitors C1 and C2 between phases A and B when simultaneously generating open-loop waveforms for both phases, which would prevent the detection of whether the neutral relay 123 is open-circuited. Furthermore, after confirming that the neutral relay 123 has no open-circuit fault, both phases of the inverter are simultaneously controlled to generate open-loop waveforms. This allows for further detection of open-circuit faults in the grid-side relays, building upon the detection of open-circuit faults in the second live relay 122. This improves the accuracy of open-circuit fault detection and enhances the safety of equipment operation.

[0095] In some embodiments, after the relay detection method outputs the first drive signal to the power conversion circuit 110 in step S110, it further includes: if the first inverter voltage does not reach the target voltage within a first preset time period, then it is determined that the power conversion circuit 110 is abnormal.

[0096] In some embodiments, after the relay detection method outputs the second drive signal to the power conversion circuit 110 in step S240, it further includes: if the first inverter voltage or the second inverter voltage does not reach the target voltage within a second preset time period, then the power conversion circuit 110 is determined to be abnormal.

[0097] When controlling the power conversion circuit 110 to output, the first grid-side voltage is used as the target output value to ensure that the voltages on both sides are consistent when the grid-side relay is closed, thus avoiding current surges caused by relay closure due to voltage inconsistencies. Therefore, when the power conversion circuit 110 is operating normally, its output first inverter voltage and second inverter voltage should ultimately be near the first grid-side voltage value. If either the first inverter voltage or the second inverter voltage fails to reach the target voltage, it indicates an abnormality in the power conversion circuit 110. Upon detecting an abnormality in the power conversion circuit 110, the power conversion circuit 110 can be shut down and an abnormality warning can be issued. The abnormality warning information can be transmitted via the alarm module in the power conversion device 100 or wirelessly to a remote terminal.

[0098] In some embodiments, the relay detection method further includes, before outputting the first drive signal to the power conversion circuit 110 in step S110:

[0099] Step 10: Control all grid-side relays to be in the off state.

[0100] Normally, all grid-side relays are in the open state during the initial startup phase or when the equipment is not started, thus preventing charging of the power conversion circuit 110 when the mains power suddenly supplies power. Therefore, if all grid-side relays are in the open state, there is no need to send a control signal to disconnect them; if there are any relays that are not disconnected, a corresponding control signal is sent to disconnect them.

[0101] Step 20: Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit 110 and the grid-side voltage corresponding to each input terminal of the AC power input terminal.

[0102] refer to Figure 1 It can acquire the first inverter voltage, the second inverter voltage, the voltage at the neutral output terminal of the power conversion circuit 110, as well as the corresponding first grid-side voltage, the second inverter voltage, and the voltage at the neutral input terminal, to detect whether there is adhesion in the A and B phase circuits.

[0103] Step 30: When the voltage difference between any grid-side voltage and the corresponding inverter voltage is less than the first threshold, it is determined that there is a sticking fault in the circuit where the grid-side relay is located, that is, there is a sticking fault in the A and B phase circuits.

[0104] When a sticking fault exists in the A and B phase circuits, it could be due to a relay sticking fault or a fault in other components within the circuit. However, regardless of the type of component sticking fault, the voltage difference between the grid-side voltage and the inverter voltage corresponding to the faulty phase will be less than a first threshold. Therefore, the presence of a sticking fault in the circuit containing the grid-side relay can be determined by detecting the voltage difference between any grid-side voltage and its corresponding inverter voltage. If the voltage differences between all grid-side voltages and their corresponding inverter voltages are greater than the first threshold, then it is determined that there is no sticking fault in the circuit containing the grid-side relay.

[0105] The first threshold is the allowable voltage difference range between the grid-side voltage and the inverter voltage under normal operating conditions. Typically, the grid-side relay closing operation is only allowed when the difference between the grid-side voltage and the inverter voltage is less than the first threshold.

[0106] In some embodiments, reference Figure 1 The first live wire relay 121, the second live wire relay 122, and the neutral wire relay 123 each include two relays connected in series. After determining in step 30 that there is no sticking fault in the circuit where the grid-side relay is located, the process further includes:

[0107] Step 31: Control all neutral wire relays 123 to close.

[0108] In some embodiments, Figure 1 The live wire relay RLY1, neutral wire relay RLY3, and live wire relay RLY5 are controlled by the Energy Management System (EMS). The live wire relay RLY2, neutral wire relay RLY4, live wire relay RLY6, precharge relay RLY11, and precharge relay RLY12 are controlled by the controller of the power conversion circuit 110. The controller of the power conversion circuit 110 is, for example, a Digital Signal Processor (DSP). In other embodiments, all grid-side relays can also be driven and controlled by the same controller.

[0109] Step 32: Control one of the first live wire relays 121 to close and the other to open and / or control one of the second live wire relays 122 to close and the other to open.

[0110] There is no strict order between steps 31 and 32. Steps 31 and 32 can be executed simultaneously, or step 32 can be executed first and then step 31.

[0111] In step 32, one of the first live wire relays 121 can be controlled to close while the other is open, and one of the second live wire relays 122 can be controlled to close while the other is open. This allows for simultaneous detection of adhesion faults in both the first and second live wire relays 121, improving detection efficiency. In other embodiments, each phase can be detected independently. That is, one of the first live wire relays 121 can be controlled to close while the other is open, and then one of the second live wire relays 122 can be controlled to close while the other is open, thus allowing for independent adhesion fault detection for each phase's live wire relays. When independently detecting adhesion faults in each phase's live wire relays, to avoid interference from potential adhesion faults in the other phase's live wires, the other phase's live wire relays can be kept in a closed state.

[0112] Step 33: Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit 110 and the grid-side voltage corresponding to each input terminal of the AC power input terminal.

[0113] The steps for obtaining this information are the same as those in step 20 above.

[0114] Step 34: When the voltage difference between any grid-side voltage and the corresponding inverter voltage is less than the first threshold, it is confirmed that at least one of the disconnect relays has a sticking fault.

[0115] If there is no relay sticking, a grid-side circuit cannot be formed due to the presence of an open first live wire relay 121 and an open second live wire relay 122. Therefore, when the power conversion circuit 110 has no power output, the voltage difference across the grid-side relays is large. If a relay sticking fault exists, a grid-side circuit is formed, and the voltage difference between the inverter voltage and the grid-side voltage is very small.

[0116] When a relay sticking fault exists, the resulting network-side circuit includes:

[0117] Phase A network side circuit: AC power supply GRID, first live wire relay 121, first inductor L1, first inverter capacitor C1 and neutral wire relay 123 (i.e. RLY3 and RLY4) to ground;

[0118] Phase B network side circuit: AC power supply GRID, second live wire relay 122, third inductor L3, second inverter capacitor C2 and neutral wire relay 123 (i.e. RLY3 and RLY4) to ground.

[0119] Therefore, taking the control of closing live wire relays RLY1 and RLY5, and opening live wire relays RLY2 and RLY6 as an example, the presence of sticking between live wire relays RLY2 and RLY6 can be detected by the voltage difference between the grid-side voltage and the corresponding inverter voltage. In one embodiment, when it is determined that there is no sticking fault in live wire relays RLY2 and RLY6, steps S32, S33, and S34 will continue to be executed. At this time, live wire relays RLY2 and RLY6 will be closed, and live wire relays RLY1 and RLY5 will be opened, so that the presence of sticking between live wire relays RLY2 and RLY6 can be detected by the voltage difference between the grid-side voltage and the corresponding inverter voltage.

[0120] That is, in this embodiment, the on / off states of the two fire wire relays in the first fire wire relay 121 and the two fire wire relays in the second fire wire relay 122 are alternately controlled to complete the detection of sticking faults in all fire wire relays. In other embodiments, one of the three fire wire relays can be controlled to be open while the other three are closed, thereby sequentially determining whether there is a sticking fault in the four fire wire relays.

[0121] In some embodiments, reference Figure 1 The relay detection method, after step 34, also includes:

[0122] Step 35: When the voltage difference between each grid-side voltage and the corresponding inverter voltage is detected to be greater than the first threshold, control both first live wire relays 121 to be closed and control both second live wire relays 122 to be open.

[0123] After detecting that the voltage difference between each grid-side voltage and the corresponding inverter voltage is greater than a first threshold, and determining that neither the disconnected first live wire relay 121 nor the disconnected second live wire relay 122 has a relay sticking fault, a control signal is sent to control both first live wire relays 121 to be in the closed state and both second live wire relays 122 to be in the open state, that is, only a single-phase live wire is controlled to be in the conducting state. In other embodiments, both second live wire relays 122 can be controlled to be in the closed state and both first live wire relays 121 to be in the open state.

[0124] Step 36: Control one of the two neutral relays 123 to close and the other to open.

[0125] There is no strict order between steps 36 and 35; the two steps can be executed simultaneously, or step 36 can be executed first and then step 35.

[0126] Step 37: Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit 110 and the grid-side voltage corresponding to each input terminal of the AC power input terminal.

[0127] In step 35, if the two first live wire relays 121 are controlled to be in the closed state, the first inverter voltage and the first grid-side voltage are detected. If the two second live wire relays 122 are controlled to be in the closed state, the second inverter voltage and the second grid-side voltage are detected.

[0128] Step 38: When the voltage difference between any grid-side voltage and the corresponding inverter voltage is less than the first threshold, it is determined that the disconnected neutral wire relay 123 has a sticking fault.

[0129] Taking the control of the two first live wire relays 121 to be in the closed state in step 35 as an example, if the neutral wire relay 123 is stuck together, the voltage difference between the first inverter voltage and the first grid-side voltage will be less than the first threshold. Therefore, this can be used to determine that the neutral wire relay 123 disconnected in step 36 has a stuck fault.

[0130] It is understandable that after determining that the disconnected neutral wire relay does not have a sticking fault, steps 36-38 are repeated. In this case, step 36 requires shutting down the neutral wire relays that have not completed the sticking fault detection. That is, by repeatedly executing steps S36-38, it can be ensured that all neutral wire relays have completed the sticking fault detection.

[0131] In some embodiments, reference Figure 1 Relay testing methods also include:

[0132] After confirming that there is no sticking fault in any of the grid-side relays, perform the step of outputting a first drive signal to the power conversion circuit 110 or outputting a second drive signal to the power conversion circuit 110; and / or

[0133] When the bus voltage of the power conversion circuit 110 is detected to be greater than the preset voltage value, the step of outputting the first drive signal to the power conversion circuit 110 or outputting the second drive signal to the power conversion circuit 110 is executed.

[0134] Understandably, the relay detection method's detection steps involve a self-test logic that is initiated after the power conversion circuit 110 is powered on. Therefore, after confirming that all grid-side relays are free from sticking faults, a soft-start output can be generated to control the first phase bridge arm and / or the second phase bridge arm of the power conversion circuit 110 to perform open-circuit fault detection on the relays. Simultaneously, to reduce the current surge from the power conversion circuit 110's output, it is necessary to ensure a certain voltage on the DC bus; that is, the power conversion circuit 110 should only be controlled to output power when the DC bus voltage has been pre-charged.

[0135] The above solution analyzes why conventional methods cannot correctly detect neutral relay faults in split-phase systems due to the presence of two-phase symmetrical inverter capacitors. It proposes a method to construct a phase-to-phase imbalance detection neutral relay during the relay self-test process. Using this method, all relay faults in the inverter can be correctly detected, greatly improving the reliability of the inverter.

[0136] It can be understood that the power conversion circuit 110 can be used as a split-phase output, which can support two-phase output, that is, the same-phase output of the first live wire and the second live wire. Whether it is a split-phase output or a same-phase output depends on the driving control of the power conversion circuit 110 according to the usage requirements.

[0137] Please continue reading. Figure 4 This application also provides a relay detection device in one embodiment, applied to a power conversion device 100. The structure of the power conversion device 100 can be found in the attached drawing. Figure 1 The relay detection device can be integrated into the power conversion device 100 or set up independently of the power conversion device 100.

[0138] Specifically, the relay detection device includes:

[0139] Control unit 401 is used to output a first drive signal to the power conversion circuit, the first drive signal being used to control the power conversion circuit to output power to the first live wire output terminal;

[0140] Acquisition unit 402 is used to acquire the first inverter voltage at the first live wire output terminal;

[0141] Control unit 401 is also used to control the neutral wire relay and the first live wire relay to close when the first inverter voltage reaches the target voltage;

[0142] The control unit 401 is also used to stop outputting the first drive signal after both the neutral wire relay and the first live wire relay are closed;

[0143] The acquisition unit 402 is also used to acquire the first grid-side voltage at the first live wire input terminal and the first inverter voltage at the first live wire output terminal;

[0144] The control unit 401 is also used to determine the fault detection results of the neutral wire relay and the first live wire relay based on the first grid-side voltage and the first inverter voltage.

[0145] In one embodiment, the control unit 401 is specifically used for:

[0146] When the voltage difference between the first grid-side voltage and the first inverter voltage is greater than the first voltage difference, it is confirmed that at least one of the neutral wire relay and the first live wire relay has an open circuit fault.

[0147] When the voltage difference between the first grid-side voltage and the first inverter voltage is less than the first voltage difference, it is confirmed that neither the neutral wire relay nor the first live wire relay has an open circuit fault.

[0148] In one embodiment, the control unit 401 is further configured to:

[0149] Control the first live wire relay to disconnect while keeping the neutral wire relay in a closed state;

[0150] A second drive signal is output to the power conversion circuit, and the second drive signal is used to control the power conversion circuit to output power to the first live wire output terminal and the second live wire output terminal.

[0151] When both the first inverter voltage and the second inverter voltage at the second live wire output terminal reach the target voltage, control all grid-side relays to close.

[0152] After all grid-side relays are closed, the output of the second drive signal is stopped;

[0153] The acquisition unit 402 is also used to acquire the first grid-side voltage of the first live wire input terminal, the second grid-side voltage of the second live wire input terminal, the first inverter voltage of the first live wire output terminal, and the second inverter voltage of the second live wire output terminal;

[0154] The control unit 401 is also used to determine the fault detection result of the second live wire relay based on the first grid-side voltage, the second grid-side voltage, the first inverter voltage, and the second inverter voltage.

[0155] In one embodiment, the control unit 401 is further configured to: determine that the power conversion circuit is abnormal if the first inverter voltage does not reach the target voltage within a first preset time period; and / or the control unit 401 is further configured to: determine that the power conversion circuit is abnormal if the first inverter voltage or the second inverter voltage does not reach the target voltage within a second preset time period.

[0156] In one embodiment, the control unit 401 is also used to control all the grid-side relays to be in an open state;

[0157] The acquisition unit 402 is also used to acquire the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal;

[0158] The control unit 401 is also configured to determine that there is a sticking fault in the circuit where the grid-side relay is located when the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold.

[0159] In one embodiment,

[0160] The control unit 401 is also configured to, after determining that there is no sticking fault in the grid-side relay:

[0161] Control the closing of all the aforementioned neutral line relays;

[0162] Controlling one of the first fire relays to close and the other to open and / or controlling one of the second fire relays to close and the other to open;

[0163] The acquisition unit 402 is also used to acquire the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal;

[0164] The control unit 401 is also configured to confirm that at least one of the disconnected relays has a sticking fault when the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold.

[0165] In one embodiment, the control unit 401 is further configured to:

[0166] When the voltage difference between each grid-side voltage and the corresponding inverter voltage is detected to be greater than the first threshold, the two first live wire relays are controlled to be closed and the two second live wire relays are controlled to be open.

[0167] Control one of the two neutral relays to close while the other opens;

[0168] The acquisition unit 402 is also used to acquire the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal;

[0169] Control unit 401 is also configured to: determine that the disconnected neutral wire relay has a sticking fault when the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold.

[0170] In one embodiment, the control unit 401 is further configured to:

[0171] After confirming that none of the grid-side relays are stuck together, the step of outputting the first drive signal to the power conversion circuit is performed; and / or

[0172] When the bus voltage of the power conversion circuit is detected to be greater than a preset voltage value, the step of outputting the first drive signal to the power conversion circuit is executed.

[0173] For details on the specific implementation method of the relay detection device and its related beneficial effects, please refer to the description of the specific embodiment of the control method for the bidirectional AC / DC converter described above; it will not be repeated here.

[0174] Please continue reading. Figure 1 and Figure 5 An embodiment of this application also provides a power conversion device 200, which in... Figure 1 The power conversion device 100 shown also includes a controller 101. The controller 101 is connected to the power conversion circuit 110 and grid-side relays, etc., and is used to execute the relay detection method as described in any of the above embodiments.

[0175] It is understood that the power conversion device 200 also includes a memory 102, a controller 101, and a computer program 103 stored in the memory 102 and executable on the controller 101. When the controller 101 executes the computer program 103, it implements the steps of the relay detection method described above.

[0176] Those skilled in the art will understand that Figure 5 This is merely an example of the power conversion device 200 and does not constitute a limitation on the power conversion device 200. It may include more or fewer components than shown, or combine certain components, or different components, such as input / output devices, network access devices, etc.

[0177] Controller 101 can be a Central Processing Unit (CPU), or it can be other general-purpose controllers, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. The general-purpose controller 101 can be a microcontroller or any conventional controller.

[0178] In some embodiments, memory 102 may be an internal storage unit of the power conversion device 200, such as a hard disk or RAM of the power conversion device 200. In other embodiments, memory 102 may be an external storage device of the power conversion device 200, such as a plug-in hard disk, smart media card (SMC), secure digital (SD) card, flash card, etc., equipped on the power conversion device 200. Furthermore, memory 102 may include both internal storage units and external storage devices of the power conversion device 200. Memory 102 is used to store operating systems, applications, boot loaders, data, and other programs. Memory 102 may also be used to temporarily store data that has been output or will be output.

[0179] One embodiment of this application also provides a power device, including a battery module and a power conversion device 200 (100) as described in any of the above embodiments. The battery module is used to supply power to the power conversion device 200 or to receive power from the power conversion device 200.

[0180] This application also provides a computer-readable storage medium storing a computer program 103, which, when executed by a controller 101, can implement the steps in the above-described method embodiments.

[0181] This application provides a computer program product that, when run on a computer, causes the computer to perform the steps described in the various method embodiments above.

[0182] It should be understood that all or part of the steps of the above embodiments can be implemented by software, hardware, firmware, or any combination thereof. When implemented in software, it can be implemented in whole or in part as a computer program 103 product. The computer program 103 product includes one or more computer instructions. The computer instructions can be stored in the above-described computer-readable storage medium.

[0183] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A relay detection method, characterized in that, The method is applied to a power conversion device; the power conversion device includes a power conversion circuit, a grid-side relay, and an AC power input terminal; the grid-side relay includes a neutral wire relay, a first live wire relay, and a second live wire relay; the first live wire output terminal of the power conversion circuit is connected to the first live wire input terminal of the AC power input terminal through the first live wire relay, the second live wire output terminal of the power conversion circuit is connected to the second live wire input terminal of the AC power input terminal through the second live wire relay, and the neutral wire output terminal of the power conversion circuit is connected to the neutral wire input terminal of the AC power input terminal through the neutral wire relay; the method includes: A first drive signal is output to the power conversion circuit, and the first drive signal is used to control the power conversion circuit to output power to the first live wire output terminal; Obtain the first inverter voltage at the first live wire output terminal; When the first inverter voltage reaches the target voltage, control the neutral wire relay and the first live wire relay to close; After both the neutral wire relay and the first live wire relay are closed, the output of the first drive signal stops; Obtain the first grid-side voltage at the first live wire input terminal and the first inverter voltage at the first live wire output terminal; The fault detection results of the neutral wire relay and the first live wire relay are determined based on the first grid-side voltage and the first inverter voltage.

2. The method as described in claim 1, characterized in that, The step of determining the fault detection results of the neutral wire relay and the first live wire relay based on the first grid-side voltage and the first inverter voltage includes: When the voltage difference between the first grid-side voltage and the first inverter voltage is greater than the first voltage difference, it is confirmed that at least one of the neutral wire relay and the first live wire relay has an open circuit fault. When the voltage difference between the first grid-side voltage and the first inverter voltage is less than the first voltage difference, it is confirmed that neither the neutral wire relay nor the first live wire relay has an open circuit fault.

3. The method as described in claim 2, characterized in that, After confirming that there is no open circuit fault in the neutral wire relay and the first live wire relay, the method further includes: Control the first live wire relay to disconnect while keeping the neutral wire relay in a closed state; A second drive signal is output to the power conversion circuit, and the second drive signal is used to control the power conversion circuit to output power to the first live wire output terminal and the second live wire output terminal. When both the first inverter voltage and the second inverter voltage at the second live wire output terminal reach the target voltage, control all grid-side relays to close. After all grid-side relays are closed, the output of the second drive signal is stopped; Obtain the first grid-side voltage at the first live wire input terminal, the second grid-side voltage at the second live wire input terminal, the first inverter voltage at the first live wire output terminal, and the second inverter voltage at the second live wire output terminal; The fault detection result of the second live wire relay is determined based on the first grid-side voltage, the second grid-side voltage, the first inverter voltage, and the second inverter voltage.

4. The method as described in claim 3, characterized in that, After outputting the first drive signal to the power conversion circuit, the method further includes: if the first inverter voltage does not reach the target voltage within a first preset time period, then determining that the power conversion circuit is abnormal; and / or after outputting the second drive signal to the power conversion circuit, the method further includes: if the first inverter voltage or the second inverter voltage does not reach the target voltage within a second preset time period, then determining that the power conversion circuit is abnormal.

5. The method according to any one of claims 1 to 4, characterized in that, Before outputting the first drive signal to the power conversion circuit, the following is also included: All network-side relays are kept in the off state. Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal; When the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold, it is determined that there is a sticking fault in the circuit where the grid-side relay is located.

6. The method as described in claim 5, characterized in that, The first live wire relay, the second live wire relay, and the neutral wire relay each include two relays connected in series. After determining that there is no adhesion fault in the circuit where the grid-side relay is located, the method further includes: Control the closing of all the aforementioned neutral line relays; Controlling one of the first fire relays to close and the other to open and / or controlling one of the second fire relays to close and the other to open; Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal; When the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold, it is confirmed that at least one of the disconnected relays has a sticking fault.

7. The method as described in claim 6, characterized in that, The method further includes: When the voltage difference between each grid-side voltage and the corresponding inverter voltage is detected to be greater than the first threshold, the two first live wire relays are controlled to be closed and the two second live wire relays are controlled to be open. Control one of the two neutral relays to close while the other opens; Obtain the inverter voltage corresponding to each output terminal of the power conversion circuit and the grid-side voltage corresponding to each input terminal of the AC power input terminal; When the voltage difference between any of the grid-side voltages and the corresponding inverter voltages is less than a first threshold, it is determined that the disconnected neutral wire relay has a sticking fault.

8. The method according to claim 1, characterized in that, The method further includes: After confirming that none of the grid-side relays are stuck together, the step of outputting the first drive signal to the power conversion circuit is performed; and / or When the bus voltage of the power conversion circuit is detected to be greater than a preset voltage value, the step of outputting the first drive signal to the power conversion circuit is executed.

9. A power conversion device, characterized in that, The power conversion device includes a power conversion circuit, a grid-side relay, an AC power input terminal, and a controller; the grid-side relay includes a neutral wire relay, a first live wire relay, and a second live wire relay; the first live wire output terminal of the power conversion circuit is connected to the first live wire input terminal of the AC power input terminal through the first live wire relay, the second live wire output terminal of the power conversion circuit is connected to the second live wire input terminal of the AC power input terminal through the second live wire relay, and the neutral wire output terminal of the power conversion circuit is connected to the neutral wire input terminal of the AC power input terminal through the neutral wire relay; the controller is used to execute the method as described in any one of claims 1 to 8.

10. An electrical device, characterized in that, It includes a battery module and a power conversion device as described in claim 9; the battery module is used to supply power to the power conversion device or receive power from the power conversion device.

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